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Old 11-02-2008, 04:55 PM   #346
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Mathij-Thanks for the post. That is a disturbing development on the use of Nitro bodies. There is nothing better looking than our 1/10 wide pan GTP bodies.

Errata Data


CRC World GT spec rear tire wear error.
My rear CRC World GT spec rear tires were wearing at half the rate that I posted. I made corrections to that post. Only .005 inch per 5 minute run. This is extremely good on the powerful wide pan.

The wide pan smoked the 1/10 Nitros again today. Some of the best local drivers were present.
John

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Old 11-03-2008, 03:45 PM   #347
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Unequal length Dynamic A-arm Front Suspension

As you know I am a fan of this kind of front suspension. What is good about it is that it controls the camber of the tire better through roll. It has less speed wasting scrub as the tire goes up into bump. That means the tire is not dragged sideways on the road as it goes up nor when the chassis rolls. It is dampened so the car does not fly off the the track at speed.
Here is the third in a series. I am hoping at one point someone will build a similar one. This one has severlal advantages over ones I previously built. This one is CRC based which provides the following advantages.

Firstly it has only a flat plate that needs to be drilled and countersunk. No milling of custom Aluminum parts. I cut it out with the dremmel wheel and sanded contours with the Dremmel Drum (wearing a respirator).

The roll center adjusts independently of camber by using the spacers that CRC provides to make roll center adjustments at the upper innner hinge pin.
A similar spacer can be used on the plastic mount below to lower the A-arm to its lowest positions. Roll center can also be adjusted at the kingpin by respacing it. Tilting the kingpin to adjust camber does not change the roll center to any extend like in the Associated type of front suspension.

The Kingpin at the wheel is fairly long to give those outer pivots generous leverage to control the camber of the tire.

Two screws remove the entire suspension for cleaning or maintenance. You can shim ride height or use the shock collars.
The suspension plate with hourglass standoffs is very stiff. No other supports are needed.

I have found that A-arms that are attached to vertical plastic mounts like the ones below the plate, will flex the mounts (in torsion on the vertical axis) intead of breaking the A-arm. These mounts look sufficiently rugged for lower A-arm abuse. The upper arm can be mounted on Aluminum so that it adds stiffness in a crash to help save the lower arm or it can be mounted on the stock plastic mounts. (Those are hugely good looking intricately machined upper A-arm mounts. I would hate to have to part with them.

The cantilevered mounts leaves generous space for the steering linkage. I have had a lot of problems clearing that with these particular A-arms.

That lower arm needs to be custom assembled but it is a brute when done so. There is a short #8 x 32 steel grade 8 stud connecting the hex Aluminum Standoff to the standard CRC upper A-arm. The middle of the A-arm (middle of the A) is then filled with a triangle of graphite sheet and powdered graphite from drilling followed by superglue. This makes a light solid arm or webbed arm. Often the failure now is the bending of that very strong steel stud. It usually can just be bent back and another drop of glue added to the joint. The hex is then joined to the standard outer ball pivot end with a short Aluminum #8 x 32 Stud. It would be nice if someone had a molded A-arm this strong in a suitable shape. I have not found one yet.

The shock will mount to the upper inner hinge pin just like on my Oval car. The lower mount can be seen in the photo.

This is going on my wide pan car which started life as a CRC Pantoura (narrow). It makes the narrow chassis wide at the front to about 214 m. The 235 mm cars are normally tapered like this.

One of my friends requested a peek so this is a spy shot of the uncompleted front end. Parts are coming to complete it. More pics to come.
John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-independent-front-suspension-crc-based.jpg  

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Old 11-03-2008, 06:18 PM   #348
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John Great Find about the Inerter.

If the gear ratios would not change, just the final flywheel tuning was chaged a cheap molded case using servo gears should work. If the Flywheel was aluminum, the Lorentz effect could be used to tune the damping. More dampening, gap the magnets closer. Less gap the magnets further.

For the device to be a decent sized replacement for pancar center shocks, I would think it would have to be about the size of the Futaba S9602 gear set.
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Old 11-03-2008, 07:17 PM   #349
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Pejota-The rules don't mention or forbid a shock. The present suspension can be dampened by a shock with a simple setup. A cantilever could be used also to attach a shock. I found the shock more effective the closer and more direct it acts on the wheel though. Here is a pic of a simple conversion to shocks. This helps but not as much as the reduced friction and improved geometry of the double wishbone. Sketch that puppy up and we can take a look at your cantilevered suspension.

Pic the car is a Powell wide pantoura chassis. Some CRC Pantoura and IRS parts, RC18T home added front and rear side shocks. Parts list available on the Pantoura thread.
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OK---I have been searching the pantoura thread for the last hour and have not found this info. (the thread is over 70 pages!) Any help in finding this post would be appreciated!
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Old 11-03-2008, 08:59 PM   #350
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mhopper-not sure which part of that post you are interested in. Here is a link to the Wide Pantoura Parts List. This list may have been used by a recent poster to that thread who is building a wide Pantoura.

http://www.rctech.net/forum/electric-road/127484-pantoura-1-10-pan-car-2s-lipo-brushless-tips-tricks-23.html#post2851931

trailranger. The inerter supplements the shock. It does not replace it. It is not meant just to dampen oscillations but to anticipate wheel events (top of the hump, bottom of the hump) much like a computerized system might try to. The size of the gear train is immaterial as long as it does not shred. I have limits to the types of servos in my dead servo drawer. The damping from eddy currents is not desired. I would have removed the magnets but it is a one piece cylindrical unit probably glued in. The ability to tune inertance is desired. I can change the lever length easily changing innertance. I can make big changes in gear ratio to change inertance possibly.

All-Think of innertance as the difficulty in spinning an armature of that mass. 1500 kg cars are using 750-1500 kg inertance. That is one heavy armature. The huge inertance is obtained by gearing a small rotating mass to the moon, well, like a servo in reverse.

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Old 11-03-2008, 10:10 PM   #351
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John how does the Inerter "predict" the end of the bump?

Each bump is providing a varied ammount of force to accellerate the flywheel

The flywheel will continue to spin until the travel is limited (Bump Stop) or the Springrate and dampner overcomes the inertia of the flywheel. At that point the Shock has to re-accelerate the Flywheel in the opposite direction to return to normal ride height.

I just don't see how that is different than just letting the inertia of the Spung weight be stoped by the Shock and rebounded by the shock.
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Old 11-03-2008, 10:18 PM   #352
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Trailranger-There is a complete mathematical solution to the oscillation control in the article that Boomer linked to. The inerter is analogous to a capacitor in The electronic circuit. It can store energy and then release it in a timely manner.

Now here is the way I see it as probably none of us are going to go through the math.

At the beginning of a bump the normal suspension reaction is for the tire to leave the ground (or overshoot the bump). The shock slows this down some, the inerter slows it down some more. Not much gained here a stiffer shock would do the same job. But the inerter gains energy here. It is spun up to speed as the tire goes up into bump.

Maximum tire contact pressure is probably at the top of the hump with the spring fully compressed. The shock is hurting here by increasing the load. The spring is hurting by increasing the load. The inerter happily gives up some energy here and raises the tire by compressing the spring an additional amount reducing tire load.

Now the back side of the bump. The inerter and wheel are up and stopped. The inerter is then spun up by the suspension spring forcing the tire down and gains energy. Near the bottom of the bump (where our pod cars are always completely out of contact with the ground in the rear at any real speed) the inerter forces the tire down from the energy stored during early downtravel of the wheel.

The goal is even tire loading throughout the bump. The inerter anticipates the top of the bump and bottom backside of the bump, something shocks cannot do. In fact shocks hurt you in these two areas.

The inertia of a heavier car would help this, but we can add 750 kg of inertance with only a 3.5 kg weight. You can see the advantage.

You predict the end of the bump by tuning the natural oscillation frequency of the suspension to the road at hand. By tuning.
john

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Old 11-03-2008, 10:26 PM   #353
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.

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Old 11-04-2008, 08:44 AM   #354
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I just wanted to share this with you guys:
http://www.youtube.com/watch?v=DxMfjw8aDMg

This is me running my 235mm Lipo-7700 Mamba MAX pro10 on a 12th scale indoor track.

Ridiculous, very scary, but what a blast to try!!
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Old 11-04-2008, 10:37 AM   #355
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I just wanted to share this with you guys:
http://www.youtube.com/watch?v=DxMfjw8aDMg

This is me running my 235mm Lipo-7700 Mamba MAX pro10 on a 12th scale indoor track.

Ridiculous, very scary, but what a blast to try!!
LOL - did you ever get past half throttle?
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Old 11-04-2008, 10:54 AM   #356
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LOL - did you ever get past half throttle?
Barely, and I still overshot just about every corner....
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Old 11-04-2008, 06:50 PM   #357
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Pro Ten- what did they use instead of boards for barriers?

John- First, when are you going to give the Inerter a try? Second, why do pan cars continue to use a kingpin style front end when it seems that a touring car style front end is possible?
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Old 11-04-2008, 08:56 PM   #358
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Pro-ten-And they said it could not be done. I guess passing would be very difficult.

Double A-arm Dampened Front End
I have one side of my independent front end finished; it is a prototype exclusively for pan car duty. It is very light. It uses existing molded parts for the most part. The carbon fibre cross-plate is very similar to a part already produced by CRC. Almost all the rest of the parts are CRC except the shocks which are RC18T shocks. The bottom arm is a glue up. The hollow in the A is completely filled. I have a photo sequence of its construction if anyone is interested. It is a brute. I changed the standoff from aluminium to plastic to add some flex in a crash. Performance on the asphalt track is already proven. It has the same suspension pickup points as my previous suspension. Here are a couple pics of the lower arm and pics of the finished suspension. A second prototype might have the dimensions slightly juggled to fit better but it came out close to perfect in appearnace and ruggedness for me. In one view of the lower arm mount you can see where it is going to twist in a crash and save that lower arm.
John

Pejota-I am doing my best effort to build one where only a few additional custom parts need to be produced. One would be a molded lower Arm. Another would be an upper shock pivot ball. A third the crossplate. Maybe if CRC is successful selling wide pan adaptor kits after a while, they could offer it as a front suspension upgrade for fast outdoor asphalt racing. The pan sector growth has been stagnant for years. This year has shown some promising growth. My hope is to offer a better front end in the future that would fit a lot of present narrow cars. This one fits the bill and changes the front to a wide car. The reason that the strut suspension is used is that it exists. No new front end parts are needed to make a 1/10 scale. I don't want a touring car front suspension. I want a nice low front suspension to fit GTP bodies or LMP bodies.

inerter test awaits a pan car with a typical center shock rear suspension. Might be soon or might not.
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-front-suspension-crc-based-003.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-front-suspension-crc-based-004.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-front-suspension-crc-based-005.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-lower-arm-construction.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-lower-arm-construction-001.jpg  

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Old 11-04-2008, 10:33 PM   #359
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[QUOTE=pejota;5015832]Pro Ten- what did they use instead of boards for barriers?
QUOTE]
Just carpet.
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Old 11-05-2008, 10:05 AM   #360
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Quote:
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John- First, when are you going to give the Inerter a try? Second, why do pan cars continue to use a kingpin style front end when it seems that a touring car style front end is possible?
There are a couple of reasons, but I think the big one is inertia/laziness - as John implied (it is used because it exists)

But here are others:

1. It is low profile. Remember, most of us use GTP style bodies which have almost zero clearance so a typical touring car style front end, with it's shock tower and suspension setup, wouldn't fit under the body.

2. It is pretty simple and it works. It's really pretty amazing what AE was able to stick in that essentially inverted strut design - dynamic camber AND caster. Easy to adjust as well - really, just keep it clean and adjust the camber as needed. . .

3. It's very strong - typically that setup will endure impacts that would shred a TC suspension.

Of course, there are weaknesses - especially the lack of dampening. . .
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